1. Field of the Invention
The present invention relates to a reclining mechanism for a vehicle seat for adjusting an inclined angle of a back rest of the seat relative to a seat cushion.
2. Description of the Prior Art
Disclosed in Japanese Patent Laid-open Publication No. 7-265154 is a reclining mechanism for a vehicle seat which is composed of a pair of lower arm members for attachment to a frame structure of a seat cushion of the seat, an upper arm member for attachment to a frame structure of a back rest of the seat, the upper arm member having a semi-circular external tooth portion formed at its lower end and being disposed between the lower arm members and connected to the lower arm members by means of a hinge pin for relative rotation about the hinge pin, a slide pawl slidably supported by the lower arm members to be moved in a radial direction with respect to the hinge pin and loaded by a spring for engagement with the external tooth portion of the upper arm member, and a release arm rotatable supported on the lower arm members to disengage the slide pawl from the external tooth portion of the upper arm member against the load of the spring.
In the reclining mechanism, the upper arm member is in the form of a single plate, while the lower arm members each are in the form of a thin sheet metal and pressed outward to form a recessed portion for containing the slide pawl. To enhance the engagement strength of the slide pawl with the tooth portion of the upper arm member, it is required to increase the thickness of the slide pawl and the upper arm member. It is, however, difficult to increase the thickness of the slide pawl and the upper arm member in such a construction of the reclining mechanism without causing any problem in manufacturing processes.